The present invention generally relates to a golf ball having a layer containing reinforced fillers. The present invention is also directed to a golf ball including a layer reinforced with fillers to increase its flexural modulus and moment of inertia.
Conventional golf balls have primarily two functional components: the core and the cover. The primary purpose of the core is to be the xe2x80x9cspringxe2x80x9d of the ball or the principal source of resiliency. The core may be solid or wound. The primary purpose of the cover is to protect the core. Multi-layer solid balls include multi-layer core constructions or multi-layer cover constructions, and combinations thereof. In a golf ball with a multi-layer core, the principal source of resiliency is the multi-layer core. In a golf ball with a multi-layer cover, the principal source of resiliency is the single-layer core.
Two-layer solid balls are made with a single-solid core, typically a cross-linked polybutadiene or other rubber, encased by a hard cover material. Increasing the cross-link density of the core material can increase the resiliency of the core. As the resiliency increases, however, the compression may also increase making the ball stiffer, thereby increasing driver spin rates. In an effort to make golf balls with improved performance characteristics, manufacturers have used thermoplastics in various layers in multi-layer golf balls. Some thermoplastic materials have a low flexural modulus, such that layers formed therefrom produce golf balls with driver spin rates at higher than desirable levels. Such high spin rates, although allowing a more skilled player to maximize control of the golf ball, can also cause golf balls to have severely parabolic trajectories and do not achieve sufficient distance. Thus, manufacturers often try to strike a balance between spin rate and distance. By adding fillers in thermoplastic layers, the flexural modulus or stiffness of such layers increases, so that the golf balls produced have lower spin rates and can achieve greater distances. However, a need still exists for a golf ball with a filled thermoplastic layer that strikes a balance between high flexural modulus (for lower driver spin) and the amount of fillers required to achieve such modulus.
Accordingly, the present invention is directed to a golf ball with a core and a polymeric layer reinforced with fillers.
The present invention is also directed to a golf ball with a layer comprising fillers embedded in a polymeric matrix to increase the flexural modulus of the thermoplastic matrix. This layer preferably also increases the rotational moment of inertia for the ball to further reduce its driver spin rate. This layer can be the cover, a portion of the cover, an intermediate layer, a portion of the intermediate layer, or any layer in the golf ball.
The present invention is directed to a golf ball comprising a core encased by an outer layer wherein the outer layer comprises a thermoplastic matrix material having flexural modulus from about 500 psi to about 30,000 psi and a filler, wherein at least about 30% by weight of the filler provides at least about 50% increase in the flexural modulus in the outer layer as compared to the unfilled thermoplastic matrix.
In accordance to another aspect of the present invention, when at least about 50% of the filler is added to the thermoplastic matrix, the flexural modulus in the outer layer is increased by at least about 90%. In accordance to yet another aspect of the present invention, when at least about 80% of the filler is added, flexural modulus in the outer layer is increased by at least about 600%.
Preferably the thermoplastic matrix material comprises a copolymer of ethylene and a carboxylic acid, wherein the carboxylic acid can be methacrylic acid, acrylic acid or maleic acid. The acid level ranges from about 3% to about 25%, more preferably from about 4% to about 15%, and more preferably from about 7% to about 11%.
Preferably, the filler comprises barium sulfate.
Preferably, the filler increases the rotational moment of inertia of the ball.
The thickness of the outer layer ranges from about 0.005 inch to about 0.030 inch, and more preferably the thickness of the outer layer is about 0.0150 inch. The outer layer can be a cover layer or an intermediate layer.